<template>
    <div class="slider" ref="slider">
        <div class="slider-group" ref="sliderGroup">
            <slot>
            </slot>
        </div>
        <div class="dots">
            <span class="dot" v-for="(item,index) in dots" :class="{active:currentPageIndex === index}" :key='index'>{{index}}</span>
        </div>
    </div>
</template>

<script type="text/ecmascript-6">
import BScroll from 'better-scroll';
import { addClass } from '@/common/js/dom';

export default {
    props: {
        loop: {
            type: Boolean,
            default: true,
        },
        autoPlay: {
            type: Boolean,
            default: true,
        },
        interval: {
            type: Number,
            default: 4000,
        },
    },
    data() {
        return {
            dots: [],
            currentPageIndex: 0,
        };
    },
    mounted() {
        // 浏览器刷新的时间是17毫秒
        setTimeout(() => {
            this._setSliderWidth();
            this._initDots();
            this._initSlider();
            if (this.autoPlay) {
                this._play();
            }
        }, 20);
        window.addEventListener('resize', () => {
            if (!this.slider) return;
            this._setSliderWidth(true);
            this.slider.refresh();
        });
    },
    destroyed() {
        clearTimeout(this.timer);
    },
    methods: {
        // 横向滚动之前需要设置Slider的宽度
        _setSliderWidth(isResize) {
            //  获取子元素的数量
            this.children = this.$refs.sliderGroup.children;
            let width = 0;
            //  获取父元素宽度
            let sliderWidth = this.$refs.slider.clientWidth;
            for (let i = 0; i < this.children.length; i++) {
                let child = this.children[i];
                addClass(child, 'slider-item');
                child.style.width = sliderWidth + 'px';
                width = width + sliderWidth;
            }
            // 循环播放的话， 会克隆两个dom 左右个一个，保证循环切换
            if (this.loop && !isResize) {
                width = width + sliderWidth * 2;
            }
            this.$refs.sliderGroup.style.width = width + 'px';
        },
        _initDots() {
            this.dots = new Array(this.children.length);
        },
        _initSlider() {
            this.slider = new BScroll(this.$refs.slider, {
                scrollX: true,
                scrollY: false,
                momentum: false,
                snap: {
                    loop: true,
                    threshold: 0.3,
                    speed: 400,
                },
                click: true,
            });
            this.slider.on('scrollEnd', () => {
                let pageIndex = this.slider.getCurrentPage().pageX;
                this.currentPageIndex = pageIndex;
                if (this.autoPlay) {
                    clearTimeout(this.timer);
                    this._play();
                }
            });
        },
        _play() {
            this.timer = setTimeout(() => {
                this.slider.next();
            }, this.interval);
        },
    },
};
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
@import '~common/stylus/variable';

.slider {
    min-height: 1px;
    position: relative;
    overflow: hidden;

    .slider-group {
        position: relative;
        overflow: hidden;
        white-space: nowrap;

        .slider-item {
            float: left;
            box-sizing: border-box;
            overflow: hidden;
            text-align: center;

            .item {
                display: block;
                width: 100%;
                overflow: hidden;
                text-decoration: none;

                .icon {
                    display: inline-block;
                    width: 100%;
                }

                img {
                    display: inline-block;
                    width: 100%;
                }
            }

            img {
                display: block;
                width: 100%;
            }
        }
    }

    .dots {
        position: absolute;
        right: 0;
        left: 0;
        bottom: 12px;
        text-align: center;
        font-size: 0;

        .dot {
            display: inline-block;
            margin: 0 4px;
            width: 8px;
            height: 8px;
            border-radius: 50%;
            background: $color-header-bg;

            &.active {
                width: 20px;
                border-radius: 5px;
                background: $color-nav-bg-active;
            }
        }
    }
}
</style>
